Plug fuse



Nov. 6, 193% N. M. STEPHENSON PLUG FUSE Original Filed Dec. 19, 1929 3 Sheets-Sheet l Inventor flormazz ifl. Stephenson.

filtorrzeyai Nov. 6, 1934. N. M. STEPHENSON 1,979,715

PLUG FUSE Original Filed Dec. 19, 1929 3 Sheets-Sheet 2 [rzvnziar flan/tan III. Stephenson.

u? Ziarneg Nov. 6, 1934; N M T P ENSO 1,979,715

PLUG FUSE Original Filed Dec. 19, 1929 3 Sheets-Sheet 3 Inventor flan/Jail lil Szaplz 6725072.

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Patented Nov. 6, 1934 UNITED STATS PATENT OFFlCE Application December 19,1929, Serial No. 415,201 Renewed March 28, 1934 27 Claims.

invention pertains to plug fuses, of the type commonly used in connection with electric lighting systems, and more particularly to fuses of the multiple, refillable type.

The general object of my invention is to pro vide a novel refillable plug fuse having a fuse element assembly or refill unit which may be easily and quickly replaced at a very nominal cost, and which comprises a plurality of fuse elements. A further object is to provide such a plug fuse having novel means for preventing arcing between adjacent fuse elements and between contact members within the fuse, when it blows.

Still another object of my invention is to provide a plug fuse of this character having novel means for preventing excessive fusing of the element and for limiting the amount of metal consumed so as to minimize the amount of gas generated by the blowing of the element.

Another object of my invention is to provide such a plug fuse in which the fuse elements are visible to determine which have been blown.

The plug fuse shown in the drawings and described herein comprises in general a body having a pair of contact members, and a replaceable fuse element assembly or refill unit detachably mounted on said body and comprising two complementary insulating members and a multiple fuse element interposed between said insulating members which serve to prevent arcing between the contact members and between adjacent individual fuse elements forming portions of the multiple element, and also to prevent excessive fusing of the fuse metal when it blows.

In the following specification will be found a more detailed description of my improvement and the manner of constructing and using the same, reference being made therein to the accompanying drawings, wherein I have illustrated my preferred specific embodiments.

Referring to the drawings,

Figure 1 is a perspective view of my improved type of fuse, shown in elevation.

Fig. 2 is a top plan view thereof.

Fig. 3 is a transverse vertical section therethrough, taken as indicated by the line 33 of Fig. 2.

Fig. 4 is a top plan View of the body portion of the plug with the fuse element assembly removed.

5 is an enlarged bottom View of the fuse element assembly.

Fig. 6 is a view similar to Fig. 5 with the barrier member removed.

Fig. 7 is an enlarged transverse sectional view taken through the fuse element assembly, as in.

Fig. 3, only showing the barrier member in spaced relation thereto.

Fig. 8 is a view similar to Figs. 5 and 6 of the carrier.

Fig. 9 is an enlarged perspective view of the fuse element in reverse position to that illustrated in Figs. 3 and 7.

Fig. 10 is a sectional view of a modified form of the fuse element assembly.

Fig. 11 is a top plan view of the form of fuse element assembly illustrated in Fig. 10.

Fig. 12 is a transverse vertical sectional view of a modified form of fuse.

Fig. 13 is a top plan view of the form of fuse illustrated in Fig. 12.

Fig. 14 is a side elevation of the form of fuse element assembly illustrated in Fig. 12.

Fig. 15 is a view similar to Fig 14, only showing the barrier member in spaced relation thereto.

Fig. 16 is a top plan view of the body illustrated in Fig. 12.

Fig. 17 is a bottom face view of the carrier illustrated in Fig. 12.

Fig. 18 is a top plan view of the barrier member.

Fig. 19 is a plan sectional view taken as indicated by the line 1919 of Fig. 14.

Referring first to Figs. 1 to 9 inclusive, the numeral 10 designates generally the body of the fuse. This may be formed of porcelain, or such other non-conductive material as may be found suitable for the purpose. Here, it is made in a substantially cylindrical configuration open at one end and is provided at its reduced lower end 11 with a metallic casing or shell 12. The shell 12 is pressed out to provide screw threads, as is commonly the case, to permit the fuse to be screwed into the usual standard socket. The body is recessed or hollow, as indicated at 13. This recess serves to lighten the structure and also provides a chamber to receive expanded gases when a fuse element is fused or blown out.

A central metallic contact member 14, preferably of tubular form, split at its upper end, extends through the lower end of the body and into the chamber 13, and is provided at its lower end with a button 15in metallic contact therewitharranged to engage one of the electrical terminals in a socket (not shown).

A second metallic contact member 16 extends through the side of the body 10 adjacent the wall thereof (see Fig. 3) and into the chamber 13. It is in metallic contact, at its lower end, with the threaded shell 12, its upper end being bent over, as at 17, to rest upon the top face of the body portion 10, this top face being slightly recessed to the thickness of the member so that the top face of this bent-over portion will lie in a plane with the top face of the body portion. The end of the bent-over portion 17 is bent upwardly, as at 18, to form a yielding spring contact with the bottom face of a fuse element, carried by a carrier, which will be more particularly hereinafter described.

The fuse element assembly mentioned above, includes two complementary insulating members, one of which is a button-shaped carrier 19 which is preferably formed of molded glass and of a size and configuration to conform to the perimeter of the upper end of the body 19. The bottom face 20 of the carrier rests upon the top face 21 of the body and a peripheral flange22 is provided thereon, the circumference of which conforms in measurement to the circumference of the upper end of the body, as illustrated in Fig. 3. The carrier is removably and rotatively retained in place on the body portion by means of a metallic band or ring 23. A plurality of spaced lugs 24 are formed upon the upper perimeter of the body, arranged to engage in complementary bayonet slots 25 cut in the band 23. The upper edge of the band 23 is turned over to engage the top face of flange 22, as shown in Fig. 3.

Suitable marking, as at 26, may be made upon the body, to indicate the position of the top 18 of the contact member 16, and a pointer 27 may be provided upon band 23, to register therewith to indicate the fuse element in contact with end 18.

The periphery of the carrier 19 may be notched, as illustrated in Fig. 1, so that it may be easily rotated with the fingers.

The carrier 19 has an annular flange 28 formed on its bottom face, adjacent the surface 20. next to which is an annular recess 29 extending upwardly into the carrier and terminating a short distance beneath its top surface 31. A plurality of radially disposed recesses or grooves 30 are also formed to extend upwardly from the top end of the annular recess 29, as shown in Fig.. 8, the

recesses 30 terminating only a short distance below the top face 31 of the carrier to form a thin wall therebetween. The latter recesses serve two purposes. I By being terminated close to the top face of the glass top, small windows 30 are provided through which portions of the fuse elements maybe viewed, and they also provide spaces, as will later appear, in which these portions may be practically segregated, to prevent arcing across from on e'to the other when the fuse element in circuit is burnt out. Recesses 32 are formed in the surface 20; flange 28 is recessed on its outer and bottom faces, as at 33 and 34;' recesses 35- extend' upwardly in the outer wall of the annular recess '29, to windows 30*, and diametrically opposed to the last mentionedrecesses are recesses 36 extending fromwindows 30 to the bottom face 37 of the central portion of the cap. Recesses 32, 33, 34, 35 and 36-are provided to receive fuse elements, generally designated by the nu- 1 reduced portion 42, adapted to extend across its r window 30 as shown in Fig. 6; a portion 43,

adapted to rest in recess 35; portions 44 and 45, adapted to rest in recesses 34 and 33, respectively; and a portion 46, adapted to rest in recess 32. The fuse portions 42 are of a reduced cross-sectional area so that the fusing will take place at these points and directly beneath the windows 36 in the recesses 30. Thus, the fuse elements may be viewed through the windows 30 from the top of the carrier, as well as those portions-which have not been fused. The fuse elements may be secured to the carrier 19 by means of an eyelet 4'7, designed to extend through a central aperture 48 in the annular portion 39 and to frictionally engage in a central aperture 49 in the carrier. A bottom peripheral flange 50, on the eyelet 47, not only retains the annular portion 39 in place, but also provides a means of making electrical contact therewith.

Each of the recesses 32 is formed of a width to receive the contact portion 46 of an arm and is of a depth slightly greater than the thickness of the metal. This increased depth is provided for the purpose of forming shoulders 52 to be engaged by the end portion 18, of contact member 16, when the fuse element is in place, to permit rotation of the carrier 19 in one direction and to prevent its rotation in the opposite direction. The opposite sides of recesses 32 may be beveled, as at 53, to more easily depress the end 18, of contact member 16, when the carrier is rotated in the proper direction.

The ends of the fuse element 38 are retained in place by a button-shaped member 51. This consists of a central tubular portion or sleeve .54, on the lower end of which is a peripheral flange 55, from the perimeter of which a flange 56 extends concentrically with the sleeve 54, forming an annular recess 57. The sleeve 54 is of a size to closely engage within the annular space 29 and the annular recess 57 is of a size as to closely receive the annular rib 28.

The length of the sleeve 54 is such that when the annular rib 28 is engaged in the annular space 57, the upper end 58 of the sleeve will abut against the top end of the annular space 29, and the reduced portions 42 of the fuse element will be closed'within the recesses 30, beneath the windows 30 By providing recesses 36 expanding gases, caused by the burning out of a fuse element, may pass downwardly into the chamber. 13 of the body 10. When the fuse element assembly is inplace on the body the bottom face of the member 51 will rest upon and be held in place by an inner annular shoulder 59, as shown in Fig. 3. Thus, the grooves in the carrier 19 are closed to form tubes or channels within which the fuse elements lie.

In the modified form illustrated in Figs. 10 and 11' the carrier 19 together with the fuse. element 38 and barrier member 51, are like those previously described, except that instead of forming the carrier entirely of glass it may be formed of other material, such as porcelain or the like, and a glass or mica disk 19 be substituted for the upper end of the glass carrier. This will provide windows as in the'other form. In such case the member 19 may be secured in place upon the carrier by means of a metallic band 60 crimped over the member 19 and around an annular flange 61, in the manner illustrated in Fig. 10. In this form the recesses which receive the upwardly extending portions of the fusible element extend entirely through the carrier and are covered by the member 19 to form the windows, as described.

In assembling the fuse, the fuse element assembly is placed upon the top surface 21 of the body 10. The band 23 is then slipped over the carrier 19 and locked in place by turning it until lugs 24 engage in bayonet slots 25, the indicator 2? being positioned above the mark 26 to indicate the particular position of the end 18 of contact member 16. In placing the carrier upon the body the upper end of contact member 14 is inserted in the bore of eyelet i7, this end, which is split for the purpose, being contracted thereby and making a close electrical contact through the sleeve 47 with the central portion of the fuse element. When it is desired to refill the fuse, the fuse element assembly is replaced.

In use, when a fuse element is burnt out, as will be indicated by the blackening of the glass of the corresponding window, it is only necessary to rotate the carrier 19 a portion of a turn to bring the end 46 of the next successive element 40 into circuit by engagement with the end 18 of contact member 16.

In the form illustrated in Figs. 12 to 19, inclusive, the body l0 may be like that previously described, provided with a lower reduced end portion li shell 12 chamber 13 and contacts 14 and 16 In this case the carrier 19 is removably secured in place by'band 23.

The carrier of this form is provided with radially extending recesses 30, 33 and 34 for receiving the fuse elements. Instead of there being a continuous annular recess for the reception of the barrier member, lateral recesses 62 may be formed in the sides of the recess 38 and instead of the barrier member 51 being in the form of a sleeve, complementary arcuate ribs 63 may be provided to extend across recess 30 and engage in recesses '62. By this means the fuse elements may be retained in place, and the individual elements electrically isolated from each other, and the size of the fuse elements gauged, as shown Fig. 19.

It is evident from the above description that when one element is blown, the fuse element assembly may be rotated to bring another element in contact with the contact members, and, when all of the elements are blown, the entire fuse element assembly or refill unit may be replaced.

While I have herein shown and described the preferred specific embodiment of my invention, I nevertheless reserve the right to make such changes or modifications in structure as will properly come within the scope of the claims appended hereto.

I claim as my invention:

1. A plug fuse comprising, in combination, a circular body having one end open, a pair of contact members, and a fuse element assembly closing the end of and attached to said body and comprising an insulating member having an indenta tion in its inner face, a fuse element connecting said contact members and having a U-shaped portion fitting in said indentation, the intermediate part of said U-shaped portion being constructed to cause the element to blow at that point, and another insulating member extending into said indentation between the legs of the U-shaped portion of the element to prevent arcing between said legs when the fuse is blown.

2. A plug fuse comprising, in combination, a circular body having one end open, a pair of contact members, and a fuse element assembly closthe open end of and attached to said body to form an enclosed chamber therein, said assembly comprising an insulating member having an indentation in its inner face, a fuse element connecting said contact members and having a U-shaped portion fitting into said indentation with a blowing point intermediate the legs of the U-shaped portion, and an insulating barrier member having a portion extending into said indentation between the legs of the U-shaped portion of the element and forming with the indented member a passage from the blowing point of the element to the chamber in the body to permit the gas generated by the blowing of the element to expand into the chamber.

3. A plug fuse comprising, in combination, a circular body, a pair of contact members, and a fuse eler ent assembly attached to said body and comprising a member made of a transparent insulating material and having an indentation in its inner face leaving a relatively thin wall between said indentation and the outer face, a fuse element connecting said contact members and having a portion bent to fit within said indentation and arranged to blow therein, and a barrier member attached to the inner face of said indented member and having a por ion fitting in said indentation, the portion of the element lying within the indentation being visible through t2 e thin wall to permit it to be seen when it blows.

4. A plug fuse comprising, in combination, a circular body having one end open, a contact member projecting centrally within the body with its free and adjacent the open end of said body, a second contact member located adjacent to the wall and the open end of said body, an insulating barrier member fitted snugly within the open end of said body to provide an insulating wall between said contact members, a fuse element connected to said contact members and bent to extend over the outer surface of said barrier member, and another insulating member attached to and closing the open end of said body and fitting snugly against the outer surface of said barrier member to enclose the element therebetween.

5. A plug fuse comprising, in combination, a

circular body having one end open, a pair of contact members, and a fuse element assembly attached to and closing the open end of said body, said assembly comprising an insulating memher having an indentation in its inner face with a groove formed in the walls of said indentation, 1

said insulating members to form a winding I" passage for said element.

'7. A plug fuse comprising, in combination, a hollow body, a pair of contact members, and a fuse element assembly attached to and closing said body, said assembly comprising two insulating members, and a fuse element connecting said contact members, one of said insulating members having a groove formed therein in which said fuse element lies and which is closed by the other of said insulating members.

LIB

8. A plug fuse comprising, in combination, a hollow body, a pair of contact members, and a fuse element assembly attached to and closing said body, said assembly comprising two insulating members, and a fuse element interposed between said insulating members and connecting said contact members, said insulating members having complementary portions forming a channel within which said element lies.

9. A refillable plug fuse comprising, in combination, a circular body having an open end, a pair of spring contact members, and a fuse element assembly detachably attached to said body comprising a carrier closing the open end of said body, a fuse element mounted on the inner face of said carrier and having its ends in contact with said spring contact members, a barrier member complementing the inner face of said carrier andproviding an insulating Wall between said contact members to. prevent arcing therebetween when the fuse blows, and means for securing said carrier to said body to hold said element in contact with said spring contact members.

-10. A refillable plug fuse comprising, in combination, a body, a pair of spring contacts, and a replaceable fuse element assembly detachably connected to said body and comprising two complementary insulating members, a fuse element interposed between said members and held in contact with said contacts, and means independ ent of the electrical circuit for detachably securing said assembly to'said body.

11. A refillable plug fuse comprising, in combination, a hollow body, a pair of contact members, and a replaceable fuse element assembly attached to and closing said body and comprising two complementary insulating members, one of said members being mounted within said body to separate said contact members, and a fuse element interposed between said insulating members for connecting said contact members.

12. A multiple plug fuse comprising, in combination, a circular body, a pair of contact members projecting within said body centrally and Y adjacent the wall thereof respectively, and a fuse element assembly rotatably attached to said body and comprising a member formed of transparent insulating material and having a plurality of radially arranged thinned portions, a plurality of radially arranged fuse elements having their blowing portions positioned adjacent the thinned portions to be visible therethrough and arranged successively to connect said contact members, and an insulating member attached to the inner face of said carrier.

13. A multiple plug fuse comprising, in combination, a circular body, a pair of spring contact members projecting within said body centrally and adjacent the wall thereof respectively, and a fuse element assembly rotatably attached to said body and comprising a carrier, an insulating member secured to the inner face of said carrier, a plurality of fuse elements interposed between said carrier and said insulating member and having their central ends joined together to form a ring, and an eyeletsecuring said ring to said carrier and enclosing the end of said central contact member, the outer ends of said elements being arranged to be brought successively in contact with the other said contact members as the fuse assembly is rotated.

14. A multiple plug fuse comprising, in combination, a hollow circular body having one end open, a pair of contact members carried by body, a plurality of radially arranged fuse olements joined at their central ends to contact with said central contact member and arranged to be brought successively in contact with said I contact member adjacent the wall of said body, and a second insulating member mounted with said body and arranged to prevent arcing between adjacent elements.

15. A multiple plug fuse comprising, in combination, a circular body, a pair of contact members carried by said body centrally and adjacent the wall thereof respectively, and a fuse element assembly attached to said body and comprising an insulating member having a plurality of indentations and radial grooves extending around the inner surfaces of said indentations and across the inner face of said insulating member, a plurality of radially arranged fuse elements arranged to be successively brought in contact with said contact members, each of said elements being bent to fit within one of said grooves, and a barrier member fitting against the inner face of said insulating member and having portions extending within said indentations to enclose said elements within said grooves and thereby segregate said elements one from another.

16. A multiple plug fuse comprising, in combination, a circular body, a pair of spring contact members located centrally and adjacent the wall of said body respectively, a fuse element assembly comprising two complementary insulating members, and a plurality of radially arranged fuse elements interposed between said members and arranged to be successively brought in contact with said contact members, and means independent of the electric circuit through the fuse for attaching said fuse element assembly to said body.

17. A multiple refillable plug fuse comprising, in combination, a circular body, a pair of contact members, and a fuse element assembly removable from said body and comprising a carrier rotatable on said body, a plurality of radially arranged fuse elements secured to said carrier and arranged to be successively brought in contact with said contact members, an insulating member secured to said carrier, a ring constructed to lock said carrier to said body by a turning motion, and means on said carrier cooperating with one of said contact members to prevent said carrier from being turned to bring a new element in contact in a direction which would unlock said ring from said body.

18. A multiple fuse element formed from a single piece of sheet-metal and comprising a plurality of radially arranged arms joined to an annular central portion forming a common terminal for all the arms, each of said arms forming an individual fuse element arranged to be used successively and comprising an S-shaped portion, the intermediate part of one loop of the S-shaped portion be- T of said boss, means for securing the central ends of said elements to said boss, and a barrier member having portions fitting within said indentations and an annular skirt fitting over the edge of said boss.

20. A fuse element assembly for a multiple refillable plug fuse comprising, in combination, a carrier formed with a hole centrally thereof, a plurality of radially arranged fuse elements joined at the central ends to form a ring, an eyelet secured in said hole and securing said ring to said carrier, and an annular insulating member attached to said carrier and holding said fuse elements against said carrier.

21. A fuse element assembly for a refillable plug fuse comprising, in combination, a carrier with a face having portions lying in different planes, a fuse element secured to and following the contour of said face and comprising terminal portions and an intermediate blowing portion lying in different planes, and an insulating member attached to said carrier and covering the blowing portion of said element.

22. In a refillable plug fuse, the combination of a hollow body having a pair of contacts, and a replaceable fuse element assembly forming a sealing closure for said body and comprising a pair of insulating members, a fuse element interposed therebetween, and means formed on said members for preventing arcing between said contacts and also between the severed portions of the fuse element when it is blown, said members providing a passage from said element to the interior of said body to permit gases to expand therein.

23. In a plug fuse, the combination of a body forming a chamber, a fuse element, and a pair of complementary members closing said chamber and forming a tortuous passage therebetween enclosing said element and opening at one end into said chamber to permit the gas generated by the blow to expand therein.

24. In a multiple plug fuse, the combination of a plurality of fuse elements having terminals at their ends, and a pair of complementary members forming a plurality of separate tortuous passages therebetween, each passage enclosing one of said fuse elements from one terminal to the other.

25. In a refillable plug fuse, a replaceable fuse element assembly comprising, in combination, a pair of button-shaped members having complementary abutting faces providing a radially positioned sinuous passage therebetween and a fuse element extending through said passage.

26. In a refillable plug fuse, a body, a pair of contact members secured in said body, one of said contact members comprising a tubular member having a split end, and a replaceable fuse element assembly comprising an insulating memher, a fuse element, and an eyelet securing said fuse element to said insulating member, said eyelet fitting over the split end of said tubular contact member to form contact therewith.

27. In a refillable plug fuse, the combination of a hollow body, and a replaceable fuse element assembly serving as a cover for one end of said body to form a closed chamber therein, said assembly comprising a pair of button-shaped members having complementary faces, and a fuse element interposed therebetween, said members providing a passage from said element to said chamber to permit gases to expand therein.

NORMAN M. STEPHENSON. 

